Radiometric and AMS graphitization laboratories are located in a building specifically designed for efficient radiocarbon dating analyses. The Radiometric division presently has 26 chemical synthesis lines and more than 65 state of the art Liquid Scintillation Counters. Beta Analytic employs the benzene method of analysis, which was in part pioneered by Dr. Tamers. The AMS division presently has 63 chemical combustion and graphitization lines, which supply Beta Analytic's Accelerator Consortium with sample graphite. The capability of large volume analysis in both the radiometric and AMS divisions was through the design of Mr. Hood. Both techniques have a practical dating range of a few hundred years to as much as 45,000 years B.R (before present, 1950 A.D.).

   Complex/Non-Standard Services* are for samples containing 0.3 to 1.0 grams of final carbon or those which require extensive specialized handling, such as organic sediments weighing more than 200 grams on arrival and bones.

   Quoted precision (the "+/- value" reported with the age of the sample) for optimal size samples generally ranges from 40-80 years for samples less than 10,000 years old. Less than optimal size samples will produce larger than normal associated standard deviations that will vary with sample size and antiquity.

  Routine AMS measurements have been performed since 1983 when Beta Analytic formed a consortium with one of the oldest and most prestigious accelerator laboratories in the world, ETH (Eidgenossiche Technische Hochschule) in Switzerland. Over the years, many accelerator facilities have requested membership in this International Consortium of AMS Laboratories. To date, we have selected six of the premier accelerator facilities as members to this consortium and have carefully intercalibrated each, to both international and in-house dating standards. This assures that all AMS dates reported from the consortium will be in agreement with the now more than 85,000 radiometric dates reported by Beta's Conventional Radiometric laboratory. All chemical treatments and target preparations are performed at Beta Analytic in our AMS graphitization laboratory. The samples are then sent by express courier to one of our Consortium Laboratories where the samples are measured and the results returned via computer link to Beta Analytic for final calculation, cross-checks and reporting.

Stable Isotope Ratios (C13/12)

  Measurement of the 13C/12C ratio allows for correction of the measured 14C age based on the amount of isotopic fractionation (enrichment or depletion) in the individual sample as compared to the modern standard. If best accuracy is needed, this ratio should be requested along with the radiocarbon dating. If the measurement is not made, one is assumed in the age calculation. For identified materials, this estimate can be very close to the measured value. However, it is especially important for unidentified plant materials which may contain a mixture of C3 (e.g. typical hardwood trees) and C4 (e.g. corn) pathway plants, and CAMS pathway plants (e.g. yucca), which could result in a 250 year error in accuracy without the measurement. It is important for bones since it will give insight into the purity of the protein extracted for analysis.

Sample Quantities Required for Analyses

   Experimentation has determined that the rate of production of radiocarbon in the earth's atmosphere is not constant. This is due to variations in the heliomagnetic modulation of the galactic cosmic radiation. Differences of several percent have been observed in the radiocarbon concentrations of contemporary plants. Dating errors, independent of statistics or laboratory procedures, caused by these variations in the sun's magnetic field, can be as much as several hundred of years. It is generally considered that four radiocarbon dates on a specific feature is sufficient to identify the occurrence of this error.